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The next step in mobility: Seamless wireless network roaming

What if users' mobile phones and/or devices could switch from a cellular carrier's wireless network to using the company's WLAN on its own, at the right time, every time?

We all appreciate the freedom and mobility afforded by the cell phone, as well as the economy and security of using the company's WLAN to download data or talk via a VoIP-based telephone system at the office.

What if users' mobile phones and/or devices could switch from a cellular carrier's wireless network to using the company's WLAN on its own, at the right time, every time -- no dropped calls, no hiccups, and no fiddling on the user's part? This "seamless wireless network roaming" is now poised to become a reality, especially with the advent of mobile computers that support multiple connectivity options. A single device can now provide wide area connections via GPRS or CDMA, WLAN connections via 802.11b, plus connectivity to Bluetooth and wired Ethernet. And it's only a matter of time before the networking and software industries catch up with the advancements in mobile hardware.

To make wireless seamless roaming happen, something needs to manage the entire communications session and the "handoff" in between networks. This requires some way to maintain the wireless connection when switching from one network to another -- going from the cellular carrier's wireless network to the enterprise's WLAN.

Because WWAN and WLAN devices require IP addresses, the most logical solution is to connect the two sessions with a specialized message router. Message routers include DHCP software to give wide area wireless devices an IP address and a network address translation (NAT) server to associate WWAN addresses to IP addresses. The message router establishes a session with both IDs and switches the ID of the session depending on which network should be used, maintaining both security and communications. In this, the router allows users to roam seamlessly, with no line drops or interruptions when switching from WWAN to WLAN. This "mobile portability" means real freedom to the mobile worker, providing almost continuous connections with the enterprise, regardless of location.

As with most technological advances, specialized message routers have their naysayers. Some don't like the idea of adding extra equipment, cost and another potential point of failure to their system. But consider this: Mobility across multiple networks will be a mainstream reality in the very near future. Wireless carriers believe in roaming (that's how we got phone number portability), and will someday provide seamless roaming capabilities among their wireless wide area networks as a subscription service; customer demand and economics will necessitate it.

Within the enterprise, roaming from cell phone when outside the office to voice over IP when within the bounds of the enterprise's wireless LAN requires the same kind of technology -- a maintained, seamless connection provided by the specialized router. For users, this means the ability to use and carry the same communication device all day. Why use a desk phone at all when your cell phone works off the company's (paid for) WLAN when inside the office?

Just consider these working scenarios:

  • For a delivery and logistics company, data roaming makes it possible to move from the warehouse (WLAN) to the delivery route (WWAN) without any intervention or interruption. Since they're financially responsible for the products on their vehicles, most route drivers typically need to check out their loads before leaving the facility.
  • Repair workers may not have the latest updates available for a specific product or procedure, but by using a single device that serves as a telephone and stores product sales information and repair manuals, service personnel can obtain updates through WWAN and/or WLAN connections (depending upon the urgency). Updates can be accessed on an "as needed" basis, without requiring a prohibitive amount of storage space for documentation that, in the end, may not even be necessary.
  • With data roaming, a delivery driver may move basic information about the work being performed back to headquarters via WWAN connections, and then drive past public hot spot locations at hotels, fast food restaurants or coffee shops to upload more detailed information (in other words, larger files) as the day goes on. The switch to the WLAN occurs in the background, without operator intervention, as the driver passes the hot spot and the device detects the availability of the faster connection.

Since the beginning of the information age, workers that do their jobs away from the office have needed a way to communicate and incorporate the results of their work with the enterprise data system. Computer networks and mobile computers were the first steps; both introduced ways to collect and deliver information from more than one location, either from inside or outside the enterprise. Seamless wireless network roaming is the next logical extension of enterprise networking technology, bringing uninterrupted communication for mobile workers, wherever they are, whenever they need to communicate.


Kelly Ungs is the Mobile Networking Product Manager at Intermec Technologies Corp., specializing in communication, networking, and software system management products to support wireless and mobile computing. He has been in the mobile computing and networking fields for 19 years designing, developing, implementing, and maintaining local and wide area wireless, mobile, and desktop computer applications and networks. He holds a Bachelor of Science from the University of Iowa in Education, and an MBA from the Keller Graduate School of Management in Kansas City, Missouri. Mr. Ungs can be reached at [email protected].

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